Evidence For Evolution

Evidence For Evolution

1. Fossils

   • A fossil is any remains or trace of a living thing from several years ago that are found in rock, soil and amber. The fossil record provides evidence of the past because when the fossils are observed closely, it helps illustrate evolutionary change throughout many years.
     • Birds evolved from small carnivorous dinosaurs known as maniraptoran theropods. Both of these animals had similar bone structure, laid their eggs the same way and had eggs that looked almost identical to one another
       • Proves that fossils represent forms of life that are extinct but can still evolve into living species
     • Scientists found a fossilized fin from a fish that was 370 million years old, with eight digits. This is comparable to the five fingers that humans have on their hands.
       • Proves an evolutionary change from sea animals to land animals.
     • A women named Mary Ann Mantell discovered a tooth, which her husband thought to be from a large iguana, but was actually the tooth of a dinosaur, Iguanodon.
       • Shows that fossils represent forms of life that do not exist anymore but may share similar characteristics to living species

2. Molecular

   • The process of the genetic material in organisms changing over time. The DNA of the organisms may molecularly evolve while the phenotypes from the ancestors remain the same.
     • Roundworms share 25% of their genes with humans.
       • These similar genes indicate that these organisms both have a common ancestor
     • Chimpanzees and humans have 96% genetic similarity
       • This proves that chimpanzees and humans must have many of the same ancestors. It also means that their DNA is very similar to one another, but as they both gradually evolved than the physical and behavior characteristics changed as well.
     • Dogs descended from the gray wolf 130, 000 years ago. The genotypes of dogs and gray wolves are identical or differ by about 0.2% mtDNA sequence.
       • This proves that certain species gradually evolved over the years to better adapt to the environment that they live in.

3. Embryology

   • An embryo is an unborn offspring in the early stages of development where its basic structures are still being formed. Embryology helps compare the embryos of living species and may suggest whether these species have a common ancestor.
     • Fish embryos and human embryos both have gill slits. In fish they eventually develop into gills, but in humans they disappear before birth.
       • This shows that fish and humans have common ancestors and possibly the same genes as the early development of these 2 organisms is very similar to one another.
     • The human embryo possesses a tail at an early development stage, just like the close primate relatives of humans do. The tail is usually reabsorbed before birth.
       • This means that humans must have a common ancestor of an animal that posses a tail, however this trait must have been lost throughout evolution as humans now do not normally have a tail at an adult stage.
     • John Vaughan Thompson proved that larval barnacles were very similar to larval shrimps as their early development stages were very much alike.
       • This means that they must have a common ancestor and inherit the same genetic plan in the development stages.

4. Biogeography

   • The study of how species were distributed around the globe. Species that are closely related are usually found living close to each other.
     • Continental Drift Theory
       • In 1915, Alfred Wegener was in shock to see that fossil plants and animals had been discovered on opposite sides of the Atlantic. Wegener figured out that the continents had once been connected, as the ocean would be too far for them to travel on their own.
     • Darwin used isolated oceanic islands (Galapagos and the Cape Verde Islands) to show how isolated environments seemed to form new species.
       • Darwin came to the conclusion that the animals that lived on the isolated islands were originally from nearby islands, but since they were separated from the species on the continent, they gradually evolved into something different over the years.
     • Marsupials of Australia. An isolated region produces different animals that are related to the nearest larger landmass.
       • A marsupial lived on the single continent. Then when it split the marsupials on the different continents gradually evolved into a species to adapt to its new environment.

5. Anatomy

   • Anatomists can identify whether a species has a common ancestor by comparing the shape, structure and relationship and identifying the similarities and differences.
     • The arm of a human, the forelimb of a giraffe, and the wing of a bat all have different functions but have a very similar bone, muscle, and nerve structure.
       • Although all 3 parts of the animals are used for different functions and look differently, they all have a common ancestor.
     • The Blue Mussels and Zebra Mussels are both “mussel shaped” and have the same function however they are distantly related to one another.
       • This shows that even though organisms may look very similar to one another and have the same function, they don’t have to come from the same ancestors.
     • Humans and apes have chests that are broader than they are deep with the shoulder blades flat in back.
       • This is due to the fact that we have evolved from an ancestor who was able to suspend itself using the upper limbs.

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